so 
SENSATION OF PLANTS. 
accounted for round slender bodies within their reach, on which so much 
by Mr.Kmght s t ress j ias fo een j a * 1( j by t jj e advocates of the existence of 
without ad* J 
witting sensa- perception and sensation in plants, have been more than 
tion ' plausibly at least, if not satisfactorily, accounted for by Mr. 
Knight, in his excellent paper on the subject, in the Philoso- 
phical Transactions for 1312 *, in which he attributes these 
effects, first to the action of light on that part of the tendril 
which is exposed to it 3 and, secondly, to the pressure which is 
made on one side by the substance round which it twines, and 
the consequent expansion of the opposite part. 
Apparent irri- The excessive irritability t (as it has been, I think, errone- 
tucc *** ^ olls] y ca ^ ec 0 of many plants, the lettuce, for instance, has 
also been often adduced in proof of the sensitive power of 
vegetables, though I must say I think without any reasonable 
foundation. I beg leave to submit, whether this supposed 
effect of irritability may not arise from the following cause : 
During the period of flowering, the vessels are so distended 
with the proper juice of the plant, that a considerable pressure 
must take place on all sides 5 so that when the plant is 
wounded, even in the slightest degree, the fluid finds an im- 
mediate, and frequently a forcible, egress. When the disten- 
tion (if I may use the term) is very great, the juice sometimes 
bursts out spontaneously, and without any previous wound 
whatever. 
Can the mo- I merely submit this for the consideration of those who 
s 10 an°l oth ° Sa ^ aVe g reater opportunities for observation, and are more inti- 
v'ery sensitive lately acquainted with vegetable physiology. Yet allow me 
plants be ex- to ask your correspondents one question — How can we, but by 
«!n sensafion ? allowing the existence of vegetable sensation, account for the 
powerful motion of mimosa sensitiva, m. niloctica, and many 
other extremely sensitive plants 3 and, indeed, numberless 
other phenomena which I should be very glad to see once more 
fairly and ably discussed ) 
I am. Sir, 
Your obedient SeTvant, 
Poole , April 6 th, 1813 . T. B« 
Vide Journal, vol. XXXtV, p. 42. 
t Vide Journal, vol. XXXII, p> 138, for M. Corradori’s experiment* 
©n the funehus ussier, &c. * . 
On 
